The present invention relates to a method and a circuit configuration to augment or preserve the driving stability of a road vehicle by controlling the traction slip by means of a brake management system.
To improve the starting behavior and the traction of a road vehicle, it is known to install devices on the vehicle which prevent spinning of the drive wheels or excessive traction slip. Such spinning tendencies occur as soon as the traction torque of the vehicle engine exceeds the torque which is transmittable through the wheels onto the road.
With rising traction slip, it is not only the torque in the driving direction that is transmittable onto the road which decreases--after having exceeded a maximum--but also the lateral guide force of the wheels decreases to a relatively very small amount. Due to this, the steerability and the driving behavior during cornering is impaired in vehicles with front-wheel drive. In vehicles with rear-wheel drive, there is even the risk of skidding when the lateral guide force is too small.
To control the traction slip, it is known from German published patent application 36 24 722 A1, which herein is referred to as an example of a great number of publications relating to systems of this type, to stabilize the imminently spinning drive wheel by way of brake management. In consideration of the temperature and the loading capacity of the brake, the period of time in which the brake can compensate for the excess torque of the drive axle is very limited. For this reason, brake management is combined with engine management in other known traction slip control systems, for instance as described in German published patent application 38 09 101 A1. However, this entails considerably greater expenditures.
DE 38 01 267 A1 teaches a vehicle brake system wherein, for augmenting the driving stability during braking on a surface with a different coefficient of friction right/left, the braking pressure is reduced on that rear wheel running on the non-skid road surface once the brake slip on this wheel exceeds a predefined value. This way, the lateral guiding force which can be generated by this wheel is increased, and swerving of the vehicle is prevented. This brake system is used instead of an anti-lock brake system.